Conventional apparatus utilizing vibrating screens for the separation of oversize particles from a liquid or wet feed stream generally include a stand, a frame movably suspended on the stand, one or more sequentially arranged screens having a total length of approximately eight feet mounted on the frame, and one or more motors mounted on the frame for vibrating the frame and attached screen. A material is deposited on the upper end of the vibrating screen or screens, which sizes and separates the oversize particles from the liquid and any undersize particles as it moves down the screen. The material is usually dropped onto the screens at approximately a right angle to the screen surface. Equipment of the type intended for separating oversize particles from a liquid or wet stream generally have a single feed and a single, or single series of cascading, planar wire cloth screens. Examples of such apparatus are described in U.S. Pat. Nos. 3,666,095 and 4,082,657 to Krynock et al. and Gage, respectively.
While conventional apparatus for separating oversize particles from a fluid or wet streams are suitable for many applications, it has been determined that for a variety of applications adequate separation can be accomplished without using the entire length of the screen or screens, since the desired separation efficiency can often be achieved by the time the material has traveled only a fraction, such as less than half, of the total length of the screen or screens. Accordingly, for many of these applications it would be highly desirable to utilize equipment of a more compact and efficient design which provides greater capacity and/or reduced equipment size. Moreover, it would be desirable to provide an apparatus for separating oversize particles from fluid or wet streams in which greater capacity and separation efficiency is achieved per unit length of the screen while providing for a single overflow discharge. Thus, although the conventional apparatus for separating oversize particles from a fluid stream often provide adequate separation for many applications, higher separation efficiency and material handling capacity for a given size of apparatus are desirable.
The conventional apparatus also have disadvantages associated with the use of wire cloth screens. In particular, cloth screens are very susceptible to wear and damage, and tend to stretch during use. Because of their susceptibility to wear and damage, frequent replacement of the screens, which is usually cumbersome and time consuming, often requires that the separation device be shut down for extended periods. Because, cloth screens tend to stretch during use, frequent adjustment of the tension on the edges of the screen is usually required or, alternatively, special means are required for maintaining adequate tension on the cloth to eliminate wrinkles, unevenness and other surface irregularities which would otherwise produce early failure of the cloth screen under the vibrating action and/or reduce separation efficiency. Accordingly, screening apparatus for separating coarse or oversize particles from a fluid or wet feed stream which utilizes a more durable screen design having an improved operating life would be highly desirable. In addition to requiring frequent replacement, cloth screens are difficult to replace as great care must be exercised during installation to ensure that the screen is free of wrinkles or unevenness. Accordingly, a more durable screen which is easy to replace is highly desirable.
Further, it would also be desirable to provide a design for a vibrating screen separating apparatus wherein the material to be separated approaches the screen surface in a direction more nearly parallel to the longitudinal plane of the screen in order to improve separation efficiency.
Therefore, the need exists for an improved wet sizing apparatus for separating oversize particles from a fluid or wet stream, which achieves improved separation efficiency, higher material handling capacity per unit length of screen while providing for a single overflow discharge, more durable, wear resistant screens, and reduced shut down time.